1. 前言

因为工作中要使用Android Camera2 API，但因为Camera2比较复杂，网上资料也比较乱，有一定入门门槛，所以花了几天时间系统研究了下，并在CSDN上记录了下，希望能帮助到更多的小伙伴。
上两篇文章们使用Camera2实现了相机预览和拍照的功能，这篇文章我们接着上文，来实现Camera2视频录制的功能。

2. 前置操作

2.1 声明相机参数和成员变量

首先还是声明相机参数和成员变量，比起前文增加了这些

private var mediaRecorder: MediaRecorder? = null
private var isRecordingVideo: Boolean = false
private val SENSOR_ORIENTATION_DEFAULT_DEGREES = 90
private val SENSOR_ORIENTATION_INVERSE_DEGREES = 270
private val DEFAULT_ORIENTATIONS = SparseIntArray().apply {
    append(Surface.ROTATION_0, 90)
    append(Surface.ROTATION_90, 0)
    append(Surface.ROTATION_180, 270)
    append(Surface.ROTATION_270, 180)
}
private val INVERSE_ORIENTATIONS = SparseIntArray().apply {
    append(Surface.ROTATION_0, 270)
    append(Surface.ROTATION_90, 180)
    append(Surface.ROTATION_180, 90)
    append(Surface.ROTATION_270, 0)
}

完整的需要声明的相机参数和成员变量如下

//后摄 : 0 ，前摄 : 1
private val cameraId = "0"
private val TAG = CameraActivity3::class.java.simpleName
private lateinit var cameraDevice: CameraDevice
private val cameraThread = HandlerThread("CameraThread").apply { start() }
private val cameraHandler = Handler(cameraThread.looper)
private val cameraManager: CameraManager by lazy {
    getSystemService(Context.CAMERA_SERVICE) as CameraManager
}
private val characteristics: CameraCharacteristics by lazy {
    cameraManager.getCameraCharacteristics(cameraId)
}
private lateinit var session: CameraCaptureSession

private lateinit var imageReader: ImageReader

//JPEG格式，所有相机必须支持JPEG输出，因此不需要检查
private val pixelFormat = ImageFormat.JPEG

//imageReader最大的图片缓存数
private val IMAGE_BUFFER_SIZE: Int = 3

//线程池
private val threadPool = Executors.newCachedThreadPool()
private val imageReaderThread = HandlerThread("imageReaderThread").apply { start() }
private val imageReaderHandler = Handler(imageReaderThread.looper)
/** Live data listener for changes in the device orientation relative to the camera */
private lateinit var relativeOrientation: OrientationLiveData

private var mediaRecorder: MediaRecorder? = null
private var isRecordingVideo: Boolean = false
private val SENSOR_ORIENTATION_DEFAULT_DEGREES = 90
private val SENSOR_ORIENTATION_INVERSE_DEGREES = 270
private val DEFAULT_ORIENTATIONS = SparseIntArray().apply {
    append(Surface.ROTATION_0, 90)
    append(Surface.ROTATION_90, 0)
    append(Surface.ROTATION_180, 270)
    append(Surface.ROTATION_270, 180)
}
private val INVERSE_ORIENTATIONS = SparseIntArray().apply {
    append(Surface.ROTATION_0, 270)
    append(Surface.ROTATION_90, 180)
    append(Surface.ROTATION_180, 90)
    append(Surface.ROTATION_270, 0)
}

2.2 添加布局

首先我们需要在XML中添加两个按钮，分别是录制按钮和停止录制按钮

<Button
    android:id="@+id/btn_capture_video"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|center"
    android:layout_marginRight="16dp"
    android:text="录屏"
    android:visibility="visible"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent" />

<Button
    android:id="@+id/btn_stop_capture"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|left"
    android:text="停止录屏"
    android:visibility="visible"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent" />

2.3 初始化MediaPlayer

我们需要在打开相机的时候，去初始化mediaPlayer

mediaRecorder = MediaRecorder()

完整代码如下

@SuppressLint("MissingPermission")
private fun openCamera(cameraId: String) {
    cameraManager.openCamera(cameraId, object : CameraDevice.StateCallback() {
        override fun onOpened(camera: CameraDevice) {
            cameraDevice = camera
            mediaRecorder = MediaRecorder()
            startPreview()
        }

        override fun onDisconnected(camera: CameraDevice) {
            this@CameraActivity3.finish()
        }

        override fun onError(camera: CameraDevice, error: Int) {
            Toast.makeText(application, "openCamera Failed:$error", Toast.LENGTH_SHORT).show()
        }
    }, cameraHandler)
}

3. 实现视频录制功能

3.1 关闭原本的Session

因为拍照和录制视频功能不好一起使用，所以需要先调用closePreviewSession，来关闭原来的session

private fun closePreviewSession() {
    session?.close()
}

3.2 给MediaRecorder设置参数

接着，需要调用setUpMediaRecorder()来初始化MediaRecorder
setUpMediaRecorder中，会给mediaRecorder设置很多预置参数

首先获取目标路径

 val nextVideoAbsolutePath = getVideoFilePath(cameraActivity)

然后设置mediaRecorder方向

val sensorOrientation = characteristics?.get(SENSOR_ORIENTATION)
val rotation = cameraActivity.windowManager.defaultDisplay.rotation
when (sensorOrientation) {
    SENSOR_ORIENTATION_DEFAULT_DEGREES ->
        mediaRecorder?.setOrientationHint(DEFAULT_ORIENTATIONS.get(rotation))
    SENSOR_ORIENTATION_INVERSE_DEGREES ->
        mediaRecorder?.setOrientationHint(INVERSE_ORIENTATIONS.get(rotation))
}

最后给meidaRecorder设置若干参数项，这里我们默认给视频尺寸设置成了1920*1080，如果你的设备相机不支持这个分辨率，需要修改一下。

mediaRecorder?.apply {
    setAudioSource(MediaRecorder.AudioSource.MIC)
    setVideoSource(MediaRecorder.VideoSource.SURFACE)
    setOutputFormat(MediaRecorder.OutputFormat.MPEG_4)
    setOutputFile(nextVideoAbsolutePath)
    setVideoEncodingBitRate(10000000)
    setVideoFrameRate(30)
    setVideoSize(1920,1080)
    setVideoEncoder(MediaRecorder.VideoEncoder.H264)
    setAudioEncoder(MediaRecorder.AudioEncoder.AAC)
    prepare()
}

再来看下完整的代码

private fun setUpMediaRecorder() {
    val cameraActivity = this

    val nextVideoAbsolutePath = getVideoFilePath(cameraActivity)

    val sensorOrientation = characteristics?.get(SENSOR_ORIENTATION)
    val rotation = cameraActivity.windowManager.defaultDisplay.rotation
    when (sensorOrientation) {
        SENSOR_ORIENTATION_DEFAULT_DEGREES ->
            mediaRecorder?.setOrientationHint(DEFAULT_ORIENTATIONS.get(rotation))
        SENSOR_ORIENTATION_INVERSE_DEGREES ->
            mediaRecorder?.setOrientationHint(INVERSE_ORIENTATIONS.get(rotation))
    }

    mediaRecorder?.apply {
        setAudioSource(MediaRecorder.AudioSource.MIC)
        setVideoSource(MediaRecorder.VideoSource.SURFACE)
        setOutputFormat(MediaRecorder.OutputFormat.MPEG_4)
        setOutputFile(nextVideoAbsolutePath)
        setVideoEncodingBitRate(10000000)
        setVideoFrameRate(30)
        setVideoSize(1920,1080) //FIXME 如果你的设备相机不支持这个分辨率，需要修改一下
        setVideoEncoder(MediaRecorder.VideoEncoder.H264)
        setAudioEncoder(MediaRecorder.AudioEncoder.AAC)
        prepare()
    }
}

3.3 重新创建Session

接着就将binding.surfaceView和recorderSurface添加到surfaces

val recorderSurface = mediaRecorder!!.surface
val surfaces = ArrayList<Surface>().apply {
    add(binding.surfaceView.holder.surface)
    add(recorderSurface)
}

重新调用cameraDevice?.createCaptureSession，将surfaces传入

cameraDevice?.createCaptureSession(surfaces,
    object : CameraCaptureSession.StateCallback() {

        override fun onConfigured(cameraCaptureSession: CameraCaptureSession) {
            //待实现
        }

        override fun onConfigureFailed(cameraCaptureSession: CameraCaptureSession) {
            Toast.makeText(application, "onConfigureFailed", Toast.LENGTH_SHORT).show()
        }
    }, cameraHandler)

3.4 开始录制

当onConfigured调用后，我们执行下面这些代码，主要执行了这些操作

• 将cameraCaptureSession赋值给session
• session?.setRepeatingRequest，这将不断地实时发送视频流，直到会话断开或调用session.stoprepeat()
• 调用mediaRecorder?.start录制视频

session = cameraCaptureSession

val previewRequestBuilder = cameraDevice!!.createCaptureRequest(TEMPLATE_RECORD).apply {
    addTarget(binding.surfaceView.holder.surface)
    addTarget(recorderSurface)
}
session?.setRepeatingRequest(previewRequestBuilder!!.build(), null, cameraHandler)

isRecordingVideo = true
mediaRecorder?.start()

3.5 录制视频完整代码

binding.btnCaptureVideo.setOnClickListener {
    startRecordingVideo()
}

private fun startRecordingVideo() {
closePreviewSession()
setUpMediaRecorder()

val recorderSurface = mediaRecorder!!.surface
val surfaces = ArrayList<Surface>().apply {
    add(binding.surfaceView.holder.surface)
    add(recorderSurface)
}

cameraDevice?.createCaptureSession(
	    surfaces,
	    object : CameraCaptureSession.StateCallback() {
	
	        override fun onConfigured(cameraCaptureSession: CameraCaptureSession) {
	            session = cameraCaptureSession
	
	            val previewRequestBuilder =
	                cameraDevice!!.createCaptureRequest(TEMPLATE_RECORD).apply {
	                    addTarget(binding.surfaceView.holder.surface)
	                    addTarget(recorderSurface)
	                }
	            session?.setRepeatingRequest(
	                previewRequestBuilder!!.build(),
	                null,
	                cameraHandler
	            )
	
	            isRecordingVideo = true
	            mediaRecorder?.start()
	        }
	
	        override fun onConfigureFailed(cameraCaptureSession: CameraCaptureSession) {
	            Toast.makeText(application, "onConfigureFailed", Toast.LENGTH_SHORT).show()
	        }
	    }, cameraHandler
	)
}

private fun closePreviewSession() {
    session?.close()
}

private fun setUpMediaRecorder() {
    val cameraActivity = this

    val nextVideoAbsolutePath = getVideoFilePath(cameraActivity)

    val sensorOrientation = characteristics?.get(SENSOR_ORIENTATION)
    val rotation = cameraActivity.windowManager.defaultDisplay.rotation
    when (sensorOrientation) {
        SENSOR_ORIENTATION_DEFAULT_DEGREES ->
            mediaRecorder?.setOrientationHint(DEFAULT_ORIENTATIONS.get(rotation))

        SENSOR_ORIENTATION_INVERSE_DEGREES ->
            mediaRecorder?.setOrientationHint(INVERSE_ORIENTATIONS.get(rotation))
    }

    mediaRecorder?.apply {
        setAudioSource(MediaRecorder.AudioSource.MIC)
        setVideoSource(MediaRecorder.VideoSource.SURFACE)
        setOutputFormat(MediaRecorder.OutputFormat.MPEG_4)
        setOutputFile(nextVideoAbsolutePath)
        setVideoEncodingBitRate(10000000)
        setVideoFrameRate(30)
        setVideoSize(1920, 1080) //FIXME 如果你的设备相机不支持这个分辨率，需要修改一下
        setVideoEncoder(MediaRecorder.VideoEncoder.H264)
        setAudioEncoder(MediaRecorder.AudioEncoder.AAC)
        prepare()
    }
}

我们运行程序，点击录制视频，过几秒点击停止录制，然后打开文件管理器，在/sdcard/Android/data/包名/files/video文件夹下，可以看到这个视频了

4. 停止录制视频

停止录制视频比较简单，只需要释放mediaRecorder
然后再调用startPreview重新开始预览就可以了

private fun stopRecordingVideo() {
    isRecordingVideo = false
    mediaRecorder?.apply {
        stop()
        reset()
    }
    //重新开始预览
    startPreview()
}

5. 实现动态设置分辨率

之前我们这是录制分辨率是写死的1920*1080，这样是不够动态灵活的，接下来我们来实现下动态设置分辨率
其实也很简单

首先通过characteristics获取到可用的分辨率列表

val characteristics = manager.getCameraCharacteristics(cameraId)
val map = characteristics.get(SCALER_STREAM_CONFIGURATION_MAP) ?:
        throw RuntimeException("Cannot get available preview/video sizes")

然后通过这个map来选择出最适合的分辨率，这里的选择规则是最高会返回1080P的分辨率

 videoSize = chooseVideoSize(map.getOutputSizes(MediaRecorder::class.java))
 
/**
 * In this sample, we choose a video size with 3x4 aspect ratio. Also, we don't use sizes
 * larger than 1080p, since MediaRecorder cannot handle such a high-resolution video.
 *
 * @param choices The list of available sizes
 * @return The video size
 */
private fun chooseVideoSize(choices: Array<Size>) = choices.firstOrNull {
    it.width == it.height * 4 / 3 && it.width <= 1080 } ?: choices[choices.size - 1]

最后，将该分辨率设置到mediaRecorder中就行了

mediaRecorder?.apply {
    setAudioSource(MediaRecorder.AudioSource.MIC)
    setVideoSource(MediaRecorder.VideoSource.SURFACE)
    setOutputFormat(MediaRecorder.OutputFormat.MPEG_4)
    setOutputFile(nextVideoAbsolutePath)
    setVideoEncodingBitRate(10000000)
    setVideoFrameRate(30)
    //setVideoSize(1920, 1080)
    setVideoSize(previewSize.width,previewSize.height)
    setVideoEncoder(MediaRecorder.VideoEncoder.H264)
    setAudioEncoder(MediaRecorder.AudioEncoder.AAC)
    prepare()
}

5. 其他

5.1 本文源码下载

下载地址 : Android Camera2 Demo - 实现相机预览、拍照、录制视频功能

5.2 Android Camera2 系列

更多Camera2相关文章，请看
十分钟实现 Android Camera2 相机预览_氦客的博客-CSDN博客
十分钟实现 Android Camera2 相机拍照_氦客的博客-CSDN博客
十分钟实现 Android Camera2 视频录制_氦客的博客-CSDN博客

5.3 Android 相机相关文章

Android 使用CameraX实现预览/拍照/录制视频/图片分析/对焦/缩放/切换摄像头等操作_氦客的博客-CSDN博客
Android 从零开发一个简易的相机App_android开发简易app_氦客的博客-CSDN博客